Time To Read
Date Last Modified
The Spinal Cord · Chapter 7 of 7
2017–2021: a waistband that burns, a bedsheet like sandpaper; “the disc is fixed, your pain should be gone.” In 2021, at forty-six, thin electrodes laid over her dorsalRelating to the back side of the body. columns turn the burning into a tingle she can walk to the mailbox with. The back pain that comes with every fever does not change. This chapter builds the gate, the cytokines that jam it, the device that closes it — and reads Chart Clue #9.
The question you will answer
Pain is first gated in the dorsal horn, not at the leg: touch fibers can close a gate there, cytokines can prop it open, a device can fire the touch fibers on purpose. Why did a correct operation leave the pain behind, and what could the stimulator reach?
Opener · The Gate · about 2½ minutes
The opener is the same narrated animation you will watch in Scene 1.
Watch the opener first. It sets the question; the chapter answers it.
1
Read the chart
Patient chart · Stina
2017–2021 · ages 42–46 · the gate, and the generator
2017–20
Allodynia: the waistband burns; a bedsheet is sandpaper. Hyperalgesia: a stubbed toe flares for hours. Post-op MRI clean. Pain clinic 2020: gabapentin, duloxetine — foggy, no better.
Labs
CRP and ESR raised on every draw since 2016; the 2017 gene panel read “negative”.
Oct 2021 · 46
Stimulator trial, seven days: leads in the dorsal epidural spaceThe space between the dura mater and vertebrae, filled with fat and blood vessels. at T9–T10, over the dorsal columns; a tingle on the left leg. Leg pain down 70%.
Nov 2021 · 46
Implant: leads anchored, a pulse generator in the right flank. The burning becomes a faint buzz; the fever-night back pain is unchanged.
Told
“The disc is fixed; your pain should be gone.” Then: “The stimulator can only reach what rides the dorsal columns.”
Chart clues this module: 1 · The picture · 2 · The paper towel · 3 · The forgiving basement · 4 · The L5 zip code · 5 · Absent means low · 6 · Where, not why · 7 · this chapter · Chart Clue #9
Before you go on · your prediction
A correct operation, a clean scan, and a leg that burns at the touch of a bedsheet. The best reading is…
Open the one you lean toward. Nothing is recorded and nothing is revealed — you come back to it at the end.
A failed surgery — something was missed and should be re-operated
Ask what a scan can photograph and what it cannot — a setting, a thresholdThe minimum voltage needed to trigger an action potential., a gain.
A difficult patient — the pain should be gone, so the problem is in her head
Ask what allodynia is, which cellsThe basic structural and functional units of life. decide how loud a pain is, and whether a cytokine can change that decision.
A sensitized dorsal horn: the disc lit the match, inflammation kept the fire burning, and the pain has become its own disease
Ask where the gate is, what closes it, what jams it, and what a device on the dorsal columns can and cannot reach.
From Stina’s diary
2
The story
Three short movements: the case, the anatomyThe study of the structure of the human body. and physiologyThe study of how the body functions., then the tie back to Stina. Each links to the scene where you’ll see it move.
I · A gate in the dorsal horn, and why rubbing a bumped elbow helps
At the tip of the dorsal horn is a layer that looks gelatinous on a fresh section A cut or slice of the body or an organ for study.: lamina II, the substantia gelatinosa — the pain gate, a structure and not a metaphor. Melzack and Wall, 1965. Pain arrives on small fibers: A-delta, thin and lightly myelinated, the sharp first pain; and C fibers, unmyelinated and slow, the burning ache that arrives second. Touch arrives on A-beta fibers — large, heavily myelinated, far faster than pain fibers, the fibers that climb the dorsal columns. Big and fast arrives first and gets to influence what follows: through inhibitory interneuronsNeurons that process information and connect sensory and motor neurons, found only in the CNS. in lamina II, the touch volley shuts down the pain signal before it reaches the spinothalamic tract. That is why rubbing a banged elbow helps. The balance at the gate decides how much reaches consciousness — pain is set in part at this synapseThe junction between two neurons where communication occurs., not at the injury. And the gate can be jammed as well as closed.
See it move: Scene 1 · The Gate · Scene 2 · Cytokines Turn Up the Volume
II · Cytokines turn up the volume
Her wiring was anatomically normal after the discectomy; what changed was the gain. Allodynia is pain from a stimulus that should not hurt — a bedsheet. Hyperalgesia is an exaggerated answer to something that should hurt a little — a stubbed toe. The umbrella is central sensitization: dorsal-horn neuronsThe functional cells of the nervous system that transmit signals. that have lowered their firing thresholds so ordinary input arrives over the line — wind-up, NMDA receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter unblocked, glia awake. No imaging modality yet invented photographs a setting. FMF kept her IL-1β and IL-6 high for decades, and those cytokines act on the superficialNear the surface of the body. dorsal horn, lowering thresholds — and blocking them eases pain after nerve-root compression. Central sensitization is measurably higher in FMF cohorts, and MEFV variants travel with fibromyalgia, the prototype sensitization syndrome. The disc lit the match; her inflammation is why the fire was still burning years after the match went out. “Your pain should be gone” quietly relocates the problem into the patient’s character. It is also bad neuroanatomy.
See it move: Scene 3 · The Generator
III · The generator, and the pain it could not reach
A knife aimed at a disc cannot reach a threshold set by chemistry, but a device can reach the gate. In October 2021, at forty-six, a pain specialist threaded two thin leads into her dorsal epidural space at T9–T10, over the dorsal columns, for a seven-day trial: pulses fire the A-beta fibers on purpose, the gate closes below, and where the burning was she felt a faint tingle — paresthesiaAbnormal sensation like tingling or numbness, often due to electrolyte imbalances.. Seventy percent less pain; the trial asks for fifty. In November the leads were anchored and a pulse generator went into her flank. Neuromodulation: change the processing, cut nothing. Her relief has a return address — the posterior column, the same white matterThe outer portion of the spinal cord made of myelinated nerve fibers that transmit signals. that delivered the problem. Then the honest part. The back pain that arrives with every fever — the prize fighter — did not change, because it never rode a root: it is serosal, inflammatory, and the generator was never aimed at it. Two pains, one gate; the device reached the one with an address in the dorsal horn. Chart Clue #9, read whole from 2026: disc fixed, root freed, pain persisted on raised markers, relieved by a gate and not a scalpel; dismissed as a failed operation and a difficult patient — in factA statement based on direct observation that is repeatedly confirmed. a systemic inflammatory disease signing its name in a new place. Her hurt outgrew its cause.
See it move: Scene 4 · Two Pains, One Gate · Scene 5 · Her Hurt Outgrew Its Cause
3
Watch · explore · think · check
5 scenes. Four have a short animation or a slide; every one has something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.
How to read the scenes
- Animation (dark teal) — a short animated explainer, one idea each
- Slide (dark teal) — a still to study: a micrograph, a diagram or a map
- Explore (purple) — something to push on while you watch
- Game (purple) — a quick challenge
- Think (gold) — reason it out, then spot-check yourself with a few true/false questions; not graded
- Check (gold) — a quick H5P that scores itself
Scene 1 of 5
The Gate
Lamina II — real cells at a real address — where touch can close the door on pain.
Animation · narrated, with captions
The Gate
Module 9 · 9.7 · Opener and Scene 1 · 8 scenes · 2½ minutes · narrated. Press Play to start; the words appear in the caption box under the picture.
Scene 1
Paused
Keyboard: when the picture has focus, Space plays or pauses, the left/right arrow keys move between scenes, and M mutes or unmutes.
Text description and full narration
Eight-scene animation, narrated by Amy Fenwick, with captions. Built from Amy’s BioRender spinal cord cross-section (Gray Matter Function), pictures from her asset library — a lower leg and foot, and an arm bent at the elbow — and the course’s IL-1β bell icon, with a drawn zoom of the dorsal horn’s layers, nerve fibers, a gate, an inhibitory interneuron, a second-order neuron, a pain meter, a threshold graph and a bedsheet.
Scene 1 · Decided in the cord (0:00–0:08)
On screen: The word “Pain”. Left: a bare lower leg and foot, with a red glow on the calf; a nerve runs from it to the right, into a BioRender cross-section of the spinal cord. Gold rings circle both dorsal horns: “first gated here: the dorsal horn”. Under the leg: “not in the leg itself”.
Narration: Pain. It's decided in the dorsal horn, not in the leg itself.
Scene 2 · Lamina II (0:08–0:18)
On screen: The cross-section shrinks to the top-left corner and a small box marks the tip of its left dorsal horn: “tip of the dorsal horn”. Lines open the box into a large zoomed panel of its outer layers: a thin dark band, a thick pale glossy band and deeper gray matter, with the label “outer layers”. On the pale band: “looks gelatinous on a fresh section”. Then the bands are labeled “I”, “lamina II” and “III–V”.
Narration: At the tip of the dorsal horn, in its outer layers, is a layer that looks gelatinous on a fresh section. It's lamina number 2.
Scene 3 · The pain gate (0:18–0:38)
On screen: The pale band is now labeled “lamina II” and “substantia gelatinosa”. A striped barrier-arm gate appears in it, hinged at the top and hanging shut: “the pain gate”, “(gate-control theory)”. Small cell bodies dot lamina II. Chips: “real cells at a real address”, “a structure, not a metaphor”, and “Melzack & Wall, 1965”.
Narration: It's called the substantia gelatinosa, and it's what we kind of, some, it's a theory, refer to it as the pain gate. It's real cells at a real address, a structure, and not a metaphor. Melzack and Wall described it in 1965.
Scene 4 · Two pain fibers (0:38–0:58)
On screen: The zoom box closes. Two thin fibers grow in from the left and end at the gate: an orange “A-delta” fiber with small, sparse myelin segments and a red “C” fiber with none. On the right, a teal “second-order neuron” reaches a dendrite up to the gate; its axon runs right and up the “spinothalamic tract” “to the brain”. Cards: “A-delta fibers”, “thin, lightly myelinated: sharp, well-placed first pain”, and “C fibers”, “unmyelinated, slow: the burning ache that arrives second”. A dot races along the A-delta fiber, the gate lifts open, and the signal passes up the tract: “1st”. A second dot crawls along the C fiber and follows: “2nd”.
Narration: Pain arrives on very small fibers, A-delta fibers, very thin, lightly myelinated, hardly, and they carry the sharp, well-placed first pain. C fibers, unmyelinated and slow, they carry that burning ache that arrives second.
Scene 5 · Touch arrives first (0:58–1:17)
On screen: A thick blue “A-beta” fiber with large myelin segments enters at the top; one branch turns up, “up the dorsal columns”, and one dives into the dorsal horn. Card: “A-beta fibers”, “large, heavily myelinated: far faster than pain fibers”. A race: an A-beta dot and a C dot leave together; the A-beta dot arrives long before the C dot: “big and fast arrives first”, “and gets to influence what follows”.
Narration: And then touch arrives on A-beta fibers, large, heavily myelinated fibers, the fastest traffic in the periphery, the same fibers that climb the dorsal columns. Big and fast arrives first and gets to influence what follows.
Scene 6 · Touch shuts the gate (1:17–1:36)
On screen: A purple “inhibitory interneuron” appears in lamina II where the A-beta branch ends. A volley of three blue touch dots reaches it; it lights up, a purple dot runs along its axon to an inhibitory ending at the gate (“−”), and the gate swings down shut: “touch shuts the gate”. A red pain dot arrives along the C fiber and stops at the closed gate: “pain signal stopped”. The second-order neuron and the spinothalamic tract are ringed in gold, but nothing travels up: “before the handoff”.
Narration: Through inhibitory interneurons in lamina 2, the touch volley shuts the gate before the pain signal is handed to a second-order neuron and up the spinothalamic tract.
Scene 7 · Rub the elbow (1:36–1:59)
On screen: Lower left: an arm bent at the elbow with an orange burst at the elbow, “a bumped elbow”, and a meter, “how much pain reaches consciousness”, standing high. A hand rubs back and forth over the elbow; blue touch dots stream along the A-beta fiber, the gate drops shut and the meter falls. A box, “fiber sizes”, shows three circles: a big myelinated A-beta, a smaller A-delta, a tiny C. Chip: “the balance at the gate decides how much reaches consciousness”. A gold ring circles the gate: “set here, in part”; by the elbow, “not at the injury”.
Narration: That's why rubbing a bumped elbow actually helps, and it's what the fiber sizes we do in this module are for. The balance at the gate decides how much pain reaches your consciousness. The amount that you feel is set in part at that synapse, not at the injury.
Scene 8 · Jammed open (1:59–2:26)
On screen: The gate swings back up and stays open: chip “a gate can be jammed as well as closed”. A ringing IL-1β bell and an IL-6 chip slide in and wedge under the lifted arm: “inflammatory cytokines”. Lower left, a graph headed “second-order neuron”: four gray bars, “ordinary input”, sit below a dashed line, “firing threshold”. The line sinks below the bar tops; the bars turn red, “over the threshold line”, and a red dot climbs the tract. Right of it, a lower leg with a pale blue bedsheet sliding across the shin, and a flame: “Stina: a bedsheet reads as fire”.
Narration: And a gate can be jammed as well as closed. Inflammatory cytokines acting on dorsal horn neurons that lowers their firing threshold for action potential. So ordinary input arrives, like, over the threshold line. And for Stina, that is like, it's like a bedsheet, reading, like, touching her and reading as fire.
Prefer the full lecture? Spinal Gray Matter (original video on the site)
Explore · in production
Open and close the gate
A dorsal horn with three input dials — A-beta touch, A-delta sharp pain, C-fiber burning — and a meter on the spinothalamic output. Predict the meter before each setting: pain alone; pain plus touch; touch first; then a cytokine dial and a bedsheet. Last: match A-beta, A-delta and C to diameter, myelin, speed and job.
Think · not graded
Big fast fibers arrive first and influence what follows. What happens to the gate in a neuropathy that thins the big fibers — the Nervous Tissue module’s stockings — and what might that predict about a touch-fiber device in her?
Spot-check your thinking: true or false?
Check · Fill in the Blanks
Set the gate.
Evidence card 1
Add it to your evidence board
A gate in the gray matterThe inner portion of the spinal cord composed mostly of neuron cell bodies and synapses. sets how loud a pain is — which is why a clean scan can sit beside a leg on fire.
Scene 2 of 5
Cytokines Turn Up the Volume
Allodynia, hyperalgesia, wind-up — and the same IL-1β and IL-6 behind every other clue, jamming the gate open.
Animation · narrated, with captions
Cytokines Turn Up the Volume
Module 9 · 9.7 · Scene 2 · 8 scenes · 2¾ minutes · narrated. Press Play to start; the words appear in the caption box under the picture.
Scene 1
Paused
Keyboard: when the picture has focus, Space plays or pauses, the left/right arrow keys move between scenes, and M mutes or unmutes.
Text description and full narration
Eight-scene animation, narrated by Amy Fenwick, with captions. Built from Amy’s BioRender spinal cord cross-section (Gray Matter Function), pictures from her asset library — a cord cross-section with a nerve root, a lower leg and foot, a receptor channel and an astrocyte — and the course’s IL-1β bell icons, with drawn jeans, bedsheet, graphs, a volume knob, microglia, a scan screen, a chart card and a match.
Scene 1 · Normal wiring, new gain (0:00–0:10)
On screen: Left: a cross-section of the spinal cord with a nerve root entering, under “Stina’s wiring, after the discectomy”, and a green check: “anatomically normal”. Right: a large volume knob labeled “gain”, from “low” to “high”. Chip: “what changed: the gain”, and the red pointer swings from low to high.
Narration: So Stina's wiring was anatomically normal after the discectomy. What changed was the gain.
Scene 2 · Allodynia (0:10–0:26)
On screen: A card: “Allodynia”, “pain from a stimulus that shouldn’t hurt”. Left: drawn hips in jeans with a red glow along the waistband: “a waistband”. Right: a lower leg; a pale blue bedsheet slides across the shin and a red glow appears under it: “a bedsheet across her shin”.
Narration: Allodynia is pain from a stimulus that really shouldn't hurt. A waistband, a bedsheet, feeling not really like fire but really more like lead, but a bedsheet across her shin.
Scene 3 · Hyperalgesia (0:26–0:37)
On screen: A card: “Hyperalgesia”, “an exaggerated answer to something that should hurt a little”. Left: a foot with an orange burst at the toes: “a stubbed toe”. Right: a graph of pain against time. A small, short gray bump: “should hurt a little”. Then a tall red curve that stays high far along the time axis: “flares for hours”.
Narration: Hyperalgesia is an exaggerated answer to something that should hurt just a little bit, a stubbed toe that flares for hours.
Scene 4 · Sensitization and wind-up (0:37–1:01)
On screen: Chip: “the umbrella: central sensitization”. Left, a graph headed “dorsal horn neuron”: four gray bars, “ordinary input”, under a dashed gold line, “firing threshold”. The line drops below the bar tops: “lowered threshold”; the bars turn red, “over the line”, and an action-potential spike draws itself: “action potential”. Right, “wind-up”: a red C fiber carries four identical volleys into a teal second-order cell; under it a bar chart, “the cell’s response”, grows taller with each volley: “fires harder each time”.
Narration: The umbrella here is called sensitization, the dorsal horn neurons that have lowered their firing thresholds so ordinary input arrives like over the line and can have an action potential. Repeated C fiber volleys, they wind the second order cell up, they wind it up so it fires harder and harder each time.
Scene 5 · Glia and a hidden setting (1:01–1:26)
On screen: Top left: a yellow receptor in a membrane, “NMDA receptor”, with a gray ball in its pore, “magnesium plug”; the ball pops out: “plug shed”. Center: a purple astrocyte touching a blood vessel, “astrocyte”, and a small drawn cell with thin branches, “microglia”; both light up, “wake up”, and IL-1β bells and IL-6 chips float out: “interleukins”. Right: a small graph whose dashed threshold line sinks lower: “threshold sinks even more”. Bottom: a dark scan screen showing an ordinary gray cord cross-section beside the gain knob in a dashed frame with a question mark: “no imaging modality yet invented photographs this setting”.
Narration: And then there's these things called NMDA receptors, they shed their magnesium plug and microglia and astrocytes, they wake up, part of the blood-brain barrier and they start pumping out interleukins and the threshold sinks even more. There's no imaging modality yet invented that photographs this setting.
Scene 6 · Where her chart joins up (1:26–1:49)
On screen: Chip: “where her chart joins up”. Left, a chart card, “Stina’s chart”: “familial Mediterranean fever” with a long bar marked “decades”, and an IL-1β bell and IL-6 chip: “IL-1β and IL-6: high”. Right: the cord cross-section with gold arcs over the tips of both dorsal horns, “superficial dorsal horn”; the bell and chip travel there. Bottom: a graph whose threshold line drops, “lower thresholds”, and a long red band, “sustain hypersensitivity”.
Narration: And here's where her chart kind of joins up. Familial Mediterranean fever keeps interleukin-1 beta and interleukin-6 very high and in Stina for decades. And those cytokines, they act on the superficial dorsal horn. They lower thresholds and they sustain hypersensitivity.
Scene 7 · What the studies say (1:49–2:19)
On screen: Card 1, “general pain neuroscience”: an IL-1β bell behind a gray blocking bar, “closest to her:” “blocking cytokines eased pain after cervical (not lumbar) nerve-root compression”, with a note “a 2010 study — not tested in Stina”. Card 2, “in FMF cohorts”: “central sensitization: measurably higher”, then “MEFV variants travel with fibromyalgia — the prototype sensitization syndrome”, and the note “fits her chart; not proof in Stina”.
Narration: This is a general pain neuroscience and closest to her with the label swapped blocking cytokines eases her pain after nerve root compression. Central sensitization is measurably higher in familial Mediterranean fever cohorts and there's different MEFV variants that travel with fibromyalgia, the prototype of sensitization syndrome.
Scene 8 · The match and the fire (2:19–2:42)
On screen: A matchstick, “the disc”, strikes and flames: “lit a match”. Beside it a large fire with an IL-1β bell: “her inflammation: why the fire is still burning”. The match flame goes out and smoke curls up, “years after the match went out”, while the big fire keeps burning. A quote card, in quotation marks: The disc is fixed. Your pain should be gone. Then: “relocates the problem to the patient’s character” and a red stamp, “bad neuroanatomy”.
Narration: So the disc kind of like lit a match. Her inflammation is why the fire is still burning years after the match went out. The disc is fixed. Your pain should be gone. It quietly relocates the problem to the patient's character. And it's also kind of bad neuroanatomy, you know.
Prefer the full lecture? Spinal Gray Matter (original video on the site)
Explore · in production
Lower the threshold
A dorsal-horn neuron with a threshold slider and a row of stimuliChanges in the environment that are detected by sensory receptors. — a feather, a waistband, a bedsheet, a pinprick, a stubbed toe. Predict which fire at the normal threshold; lower it with a cytokine dial and predict again, naming allodynia and hyperalgesia before the label. Then wind-up. Last: sort the evidence cards into general pain biology and FMF-specific.
Think · not graded
Her scan was clean, her markers were high, and a bedsheet hurt. Say in one sentence what kind of problem that is, and why “inflamed” is a different word, a different mechanism and a different diagnosis from “imagined”.
Spot-check your thinking: true or false?
Check · Multiple Choice
Select the three terms that name her pain state.
Evidence card 2
Add it to your evidence board
Allodynia and hyperalgesia with high inflammatory markers after a clean decompression: the gate propped open by chemistry.
Scene 3 of 5
The Generator
Leads over the dorsal columns, a trial, an implant at forty-six — gate-control theoryA well-tested and widely accepted explanation. you can switch on.
Animation · narrated, with captions
The Generator
Module 9 · 9.7 · Scene 3 · 8 scenes · 1¾ minutes · narrated. Press Play to start; the words appear in the caption box under the picture.
Scene 1
Paused
Keyboard: when the picture has focus, Space plays or pauses, the left/right arrow keys move between scenes, and M mutes or unmutes.
Text description and full narration
Eight-scene animation, narrated by Amy Fenwick, with captions. Built from Amy’s BioRender pictures — a herniated disc seen from above, the spinal cord stimulator back view (its own leads and labels removed so the leads could be redrawn at T9–T10), the remote control, the lower-body outline seen from behind, and the cord cross-section (Gray Matter Function) — plus a scalpel from her asset library and the course’s IL-1β bell icon, with a drawn dial, leads, side-view diagram of the cord, pain diary and relief bar.
Scene 1 · Out of a knife’s reach (0:00–0:07)
On screen: Left: a BioRender vertebra seen from above with a disc bulging toward a nerve root, and a scalpel aimed at it: “a knife aimed at a disc”. Right: a dial labeled “threshold”, with an IL-1β bell and an IL-6 chip beside it: “a threshold reset by chemistry”. A dashed arrow from the scalpel toward the dial stops short at a red X: “cannot reach”.
Narration: A knife aimed at a disc cannot reach a threshold reset by chemistry.
Scene 2 · Leads at T9–T10 (0:07–0:26)
On screen: Left: Amy’s BioRender back view of the spine and ribs. Chips: “a device can reach the gate” and “age 46”. Two thin leads are threaded up the midline from the lower back and stop at the levels marked “T9” and “T10”, each tip carrying four metal contacts: “two thin leads”. Right: a cross-section of the cord inside a dashed ring, the dura; the two leads sit just outside it at the back: “dorsal epidural space”. The dorsal columns shade blue: “right over the dorsal columns”. A bracket on the back view runs from T10 down to “her L5 roots”: “several segments above her roots”. A strip of seven numbered boxes: “seven-day trial”.
Narration: A device can reach that gate, though, and at 46, a pain specialist threaded two thin leads into Stina's dorsal epidural space at T9, T10, right over the dorsal columns, several segments above her roots, and they ran a seven-day trial.
Scene 3 · Pulses close the gate (0:26–0:40)
On screen: A side-view diagram of the cord, back on the left and front on the right, with bands labeled “dorsal columns”, gray matter and “spinothalamic tract”. A lead lies outside the dura at the back, “lead, T9–T10”. Low down, “her L5 root” brings a blue A-beta fiber that turns up the dorsal columns, and a red C fiber that ends at a small gate. Rings pulse from the lead; blue dots run down the A-beta fiber “a few segments below” to a purple interneuron, and the gate swings shut; a red pain dot stops at it. Chips: “pulses fire A-beta fibers”, “on purpose”, “lamina II interneurons close the gate”; the seven-day strip moves to the right-hand column.
Narration: The pulses, they fire A-beta fibers, they fire them on purpose, and the inhibitory interneurons in lamina II, they close their gate a few segments below.
Scene 4 · Home from the trial (0:40–0:54)
On screen: A back view of both legs. A red stripe runs down the back of the left leg, “pain down the back of her leg”, and the left foot glows red, “crushing feeling in her foot”. Chip: “home from the trial”, with a teardrop: “she cried”. Both fade: “nearly all gone”. Gold dots spread along the same stripe and foot: “replaced with a tingle (paresthesia)”.
Narration: When she got home from the implantation of the trial leads, she cried. The pain down the back of her leg, the crushing feeling in her foot, it was all gone. It was just replaced with the most wonderful tingle.
Scene 5 · The pain diary (0:54–1:04)
On screen: A notebook page, “pain diary”, with a 0–10 scale: four days before the trial sit at 8 and 7, then the seven trial days drop to 2 and 3. Big numbers: “8” then “2”. A relief bar fills to 70% past a marker at 50%: “about 70% relief” and “the usual bar: 50%”.
Narration: Her pain diary dropped from like 8 to like 2. 70%, well past the 50 the trial requires.
Scene 6 · The implant (1:04–1:21)
On screen: Chip: “November: the implant”. The BioRender back view again, now down to the pelvis, with the two leads at T9–T10, gold anchor marks where they enter, “leads anchored”, and an extension wire to a pulse generator, ringed in gold: “pulse generator: right flank”. A BioRender remote control: “remote: in her pocket”. Right: chips “neuromodulation”, “change the processing” with a check, and a scalpel struck through: “cut nothing in the cord”.
Narration: So in November, her leads were anchored with a pulse generator, and it went right into her right flank with a remote that she could get in her pocket. That is neuromodulation. Change the processing. Don't cut anything in the cord.
Scene 7 · Back of the cord, front of the cord (1:21–1:31)
On screen: A large cross-section of the cord. Two leads sit at the back in the epidural space: “device: on the back of the cord”. Both spinothalamic tracts, at the front, glow red: “pain arriving at the front: the spinothalamic tract”. Chip: “the gate account explains it”. Blue dots run from the leads into the dorsal columns and to the tips of the dorsal horns, where small gates swing shut, “the gate (lamina II)”, and the red tracts fade: “the tract is not cut or blocked — it is quieted at the gate”.
Narration: Only the gate account explains why a device sitting on the back of the cord can quiet pain arriving at the front of it.
Scene 8 · Riding the posterior column (1:31–1:42)
On screen: The same cross-section; the dorsal columns at the back glow blue: “posterior (dorsal) columns: white matter”. Chip: “her relief rides the posterior column”.
Narration: Her relief, it rides that posterior column, the same white matter that delivered the problem in the first place.
Prefer the full lecture? Sensory Spinal Pathways (original video on the site)
Explore · in production
Place the leads
A sagittal spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae.. Drag the leads to where they must sit — which space, surface and level — and say which fibers they fire. Run the seven-day trial with a pain-diary slider: does 70% pass the 50% rule? Switch tonic, burst and 10 kHz and predict which she feels. Last: predict which of her pains the device can reach.
Think · not graded
The device sits on the back of the cord and quiets pain arriving at the front. Which mechanism survives that — blocking the spinothalamic tract, or firing the dorsal columns to close the gate? What does the Nervous Tissue module’s neuropathy predict about her big fibers?
Spot-check your thinking: true or false?
Check · Multiple Choice
The stimulator relieves her leg pain by…
Evidence card 3
Add it to your evidence board
A device that reaches the gate helped where a scalpel could not — so the pain was never purely structural.
Scene 4 of 5
Two Pains, One Gate
The stimulator softened the leg; the prize-fighter back pain kept the fever’s schedule.
Slide · in production
Why Surgery Did Not Fix It — and What the Generator Could Not Reach
Two different causes, wearing one symptom — and a third pain that was never a spine story at all.
Prefer the full lecture? Sensory Spinal Pathways (original video on the site)
Game · in production
Three pains, three causes
Three pain cards — the 2015 stripe, the 2017 burning, the fever-night back — and three causes: a compressed root, a sensitized dorsal horn, an inflamed serosa. Sort before the key, then match discectomy, stimulator and colchicine to the pain each can reach. Last: write the sentence the 2017 clinician should have written instead.
Think · not graded
Conflate the cause of an injury with the cause of ongoing pain and you dismiss someone like her. State both causes for her leg, add the third pain, and say why the generator never changed it.
Spot-check your thinking: true or false?
Check · Summary
Choose the correct statement in each set.
Evidence card 4
Add it to your evidence board
The device reached the pain with an address in the dorsal horn; the pain with a fever’s schedule was never a spine story.
Scene 5 of 5
Her Hurt Outgrew Its Cause
The spine chart on one page: disc, surgery, sensitization, stimulator, and a fever nobody aimed at — Chart Clue #9.
Prefer the full lecture? Sensory Spinal Pathways (original video on the site)
Explore · in production
The chart on one page
A three-column ledger — mechanical, inflammatory, set aside — and ten finding cards from 2010 to 2021. Sort before the key, naming the cell or lane the cytokines reached for each inflammatory card. Last: write Chart Clue #9 in one sentence.
Think · not graded
Line by line, her spine chart reads as a treatment failure, a difficult patient and a compensation issue — and it was read all three ways. Read whole, what is it, and which of her three pains was each clinician looking at?
Spot-check your thinking: true or false?
Check · Multiple Choice
Chart Clue #9 reads her spine story as…
Evidence card 5
Add it to your evidence board
Disc fixed, root freed, pain outgrew its cause, relief from a gate and not a knife, and a fever-night back pain untouched by any of it: Chart Clue #9.
4
Your evidence board
Every scene gave you an evidence card, and the chart adds more. Sort each card into the column it supports: Cytokine-driven central sensitization — plus an inflammatory back pain the spine never explained, Neither on its own, or A failed surgery, a difficult patient, or a disc not fully fixed. Some cards can honestly go in more than one place — that’s allowed, and the feedback tells you which cards decide the case.
5
Your verdict
Time to decide. Look back at your bet, then build your verdict from statements that hold up — no writing needed.
Look back at your prediction
A correct operation, a bedsheet that burns, a tingle that helps, and a back that keeps a fever’s schedule — the reading that fits best is…
Find the one you chose at the top. Does the evidence support it, refute it, or revise it?
- A failed surgery — something was missed and should be re-operated
- A difficult patient — the pain should be gone, so the problem is in her headRounded proximal end that fits into the acetabulum of the hip bone.
- A sensitized dorsal horn: the disc lit the match, inflammation kept the fire burning, and the pain has become its own disease
Build your verdict · no writing
Choose the statement that holds in each set. The ones you keep become your argument.
6
The finding
Finding · Chart Clue #9
Her Hurt Outgrew Its Cause
2015–2021: a disc fixed and a root freed; allodynia, hyperalgesia and a clean scan; CRP and ESR high on every draw; in 2021, at forty-six, a stimulator over the dorsal columns that traded the burning for a tingle — and a back pain on a fever’s schedule that no spine treatment touched. Chart entry: the gate in lamina II, closed by A-beta touch and jammed by IL-1β and IL-6; central sensitization as pain that has become its own disease; relief from neuromodulation that fits a pain that was never purely structural. Read whole, from 2026: a systemic inflammatory disease signing its name in a new place. Chart Clue #9.
Next · Module 10
The Brain
If inflammation can rewire the cord, what does it do one level up? A radiologist noted “a few nonspecific white spots — more than expected for age” and suggested migraine. Nobody asked what was driving them, or what the barrier that should keep inflammation out was doing. The next module goes upstairs.
Reliable information on rare diseases
NORD · NIH GARD · Orphanet · MedlinePlus Genetics: FMF · FMF & AID Global Association · Autoinflammatory Alliance · Global Genes · Amyloidosis Foundation
Stina has one rare disease. In the United States, about 1 in 10 people live with one of the more than 7,000 known rare diseases. These organizations are where patients, families and clinicians go for trustworthy information.
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← Familial Mediterranean Fever — case home
All pages for Module 9 — The Spinal Cord
9.0 Module Overview
9.1 The Disc That Finally Had a Picture
9.2 Inside the Cable
9.3 Three Wrappers and a Needle
9.4 Roots to Skin
9.5 The Five-Dollar Localizer
9.6 Highways With Names
9.7 The Gate and the Generator
9.8 Conclusion and Assessment
9.9 Evidence Behind the Case
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- dorsal
- epidural space
- threshold
- cells
- anatomy
- physiology
- section
- interneurons
- synapse
- neurons
- receptors
- superficial
- paresthesia
- white matter
- fact
- gray matter
- stimuli
- theory
- spine
- head
- development